Manufacture of rectifier disks



Sept. 28, 1948.

E. A. RICHARDS :fr/M.y

IANUFACTURE 0F RECTIFIER DISKS Filed Nov. 20, 1943 Patented Sept. 28,1.948

2,450,020 MANUFACTURE oF Boorman msxs Edward Arthur Richards, LeslieJames Ellison, and Frank Gray, London, England, assignors, by mesneassignments, to International lStandard Electric Corporation, New York,N. Y., a

corporation oi Delaware Application NovemberZO, 1943, Serial No. 511,103In Great Britain December 3, 1942 3 calms. (ci. irs- 366) called centrecontact construction described in' British Patent No. 526,482, x

The present invention provides a process for the manufacture ofapertured rectier elements by cutting or blanking them out from arelatively large sheet metal base plate provided with a layer ofrectifying material to which a conducting layer forming thecounterelectrode is applied, and is characterised in this that before4the conducting layer is applied the base plate is provided with aplurality of holes corresponding to the apertures in the elements to beout therefromand these holes are masked during the application of theconducting layer to leave a clear space at the periphery of each holeand so avoid the necessity of subsequent trimming. Preferably the holesare masked by inserting mushroom-shaped elements therein.

In applying the process to the manufacture of so-called centre contactrectifier elements a layer of insulating material is applied to thelayer of rectifying material to cover a small area around each holeeither before or after the holes are out in the plate.

The above and other features of the invention will be better understoodfrom the following description of one particular embodiment thereof withreference to the accompanying drawings, in which Fig. 1 is a plan viewof a portion of a selenium coated base plate with a portion of thecoating removed; p

Fig. 2 is a sectional elevation thereof;

Fig. 3 shows the plate pierced with centre holes;

Fig. 4 shows a mushroom-shaped mask for masking the centre holes;

Fig. 5 shows the pierced plate of Fig. 3 with the masks in position andcoated with counterelectrode metal, indicating in dotted lines the discsto be blanked out therefrom;

Fig. 6 shows the plate with a coating of insulating material around thecentre holes as used in the manufacture of the so-calied centre-contactdiscs:

2 Fig. 'l shows the plate coated with counter-electrode metal with themushroom-shaped masks in position: and Fig. 8 is a view of one of theblanked-out discs.

Referring to Figs. 1 and 2, a sheet of steel or.

other metal forming the base plate A is coated with a layer of seleniumB over the whole of one surface, and the appropriate heat treatment isapplied to the selenium to convert it to the alpha modification. Thesheet is then pierced with a number of holes C correspondingto thecentreY holes of the small discs which are eventually to be punched fromthe larger sheet, as shown in Fig. 3. Mushroom-shaped masks D (1013.4)are then placed in the holes, and the Whole sheet is sprayed withcounter-electrode metal E as shown ln Fig. 5. The masks leave therectiiying layer exposed around the periphery of the holes in the sheetso that there is no possibility of short-circuit between thecounter-electrode metal and the base plate. The necessary electricalforming process is preferably carried out before the small Idiscs arepunched from the larger sheet, and for this purpose the edge of the.sheet is masked as indicated at F to prevent short-circuiting with thebase plate. If desired, the small discs can. be electrically formedindividually after geing cut from the base plate. The dotted lines Gshown in Fig. 5 indicate the outer periphery of the discs to beeventually cut from the plate.

In the manufacture of the so-called centrecontact discs, the base plateis placed in a mask provided with holes of a diameter larger than the'holes C in the sheet, and a suitable insulating varnish or enamel issprayed on to the portions of the sheet thus exposed. In this manner thesurface surrounding each centre hole is coated with the insulatingenamel over an area determined by the size of the holes in the mask asindicated in Fig. 6, wherein H represents the in- -sulating coatingaround the holes. It will be understood that this insulating coating maybe ap plied either before or after the holes C are out in the plate. Thesheet may then pass through a further heat treatment to convert theselenium to the beta form, and at the same time to bake the enamelportions H to the required degree of hardness. The mushroom-shaped masksD are then inserted in the holes and the counter-electrode metal sprayedon as previously described and as shown in Fig. 7. This leaves theinsulating enamel H exposed around the periphery of the holes in thesheet so that there is no possibility of` short circuit between thecounter-elec- 4 trode metal and the base plate, it being under- I stoodthat the mushroom-shaped masks are of such a size that thecounter-electrode metal extends over a portion of the insulating ringsH.

After the sheets have beenrprepared as abovedescribed either for themanufacture of centrecontact type or non-centrecontact type, discs ofthe required diameter may then be cut or blanked out from the sheetusing the centre holes as a guide. Fig. 8 shows one of the blanked outdiscs in which J represents the clear area left around the centre holeC. The counter-electrode metal at the outside edge of the blanket-outdiscs may be removed by cutting a groove or by shot-blasting in themanner described in previous United States applications numbers 509,109and 508,225, both now abandoned. As an alternative to spraying the wholesurface of the plate with counterelectrode metal except for the ringaround the centre holes, a second mask may be used to limit thecounter-electrode metal to the working surface of each small disc. Thiswould leave the selenium exposed at the outside edge Where the punchingoperation takes place, and thus avoid the need for removing thecounter-electrode metal from the edge after the discs have been blanked.With this arrangement, however, it is not possible to form the wholesheet electrically unless special contacts are arranged to connect toeach small disc separately, but as above indicated, the discs can beformed separately after blanking out.

The process has been described as applied to the manufacture of circulardiscs from a rectangularsheet. but lt'will be obvious that any othershape may be used either for the original sheet or for the nalrectiflers, and that the small rectiers may be produced by a cuttingoperation instead of punching' as described. Moreover, al` though theaperture has been referred to as a centre hole, it will be understoodthat this may be otherwise located or may take the form of a slot.

What is claimed is:

1. A process of manufacturing a plurality of apertured so-calledcenter-contact rectifier elements from a base plate provided with alayer of rectifying material which comprises the following steps:punching out a plurality of holes corresponding to the holes in theelements to be made, applying insulating material to the layer ofrectifying material to cover a small area around each hole, insertingself-centering masks in these-holes, spraying the base plate with aconducting layer forming the counter-electrode, covering the masks andthe exposed surface of the rectifying layer.

2. A process of manufacturing apertured rectifler elements from a baseplate provided with a layer of rectifying material which comprises thefollowing steps: punching out a plurality of holes corresponding to theholes in the elements to be made, inserting self-centering masks inlthese holes, spraying the base plate with a conducting layer, formingthe counter-electrode covering the masks and the exposed surfaces of therectifying layer, severing the elements from the said base plate, andremoving the conducting layer at the outer edges of the blanked-outreotiiier elements by shot-blasting.

3. A process of manufacturing apertured rectier elements from a baseplate provided with a layer of rectifying material which comprises thefollowing steps: punching out a plurality of holes corresponding to theholes in the elements to be made. inserting self centering masks inthese holes, spraying the base plate with a conducting layer forming thecounter-electrode covering the masks and the exposed surfaces of therectifying layer, and subjecting the sheet-metal base plate, therectifying layer, and the conducting layer to an electrical formingprocess before the individual rectifier elements are cut therefrom.

EDWARD ARTHUR RICHARDS.

LESLIE JAMES ELLISON.

FRANK GRAY.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number

